As the resin which yields a material having flexibility, thermoplastic resins such as soft polyvinyl chlorides, polyethylenes and polypropylenes have been conventionally used. However, these thermoplastic resins have insufficient heat resistance and, especially, are not suitable for use at high temperatures over a long period of time.
As heat-stable materials having flexibility, vulcanized rubbers are widely employed. However, the vulcanized rubber needs vulcanization steps after shaped by molding, calendaring or extruding.
Vulcanization requires a complicated control of the reactions to keep sufficient softness and to constitute a three-dimensional crosslinking structure. The reactions must be controlled by combining various vulcanizations-accelerators and scorch retarders. In addition, the vulcanization process must be performed at high temperatures and requires a long period of time.
On the other hand, some of silicone rubbers are cured or vulcanized at ambient temperature (RTV silicone rubbers), in which two components which are liquid at room temperature are mixed in a specific ratio to thereby cure the component rubbers. The cured articles of RTV silicone rubbers have excellent heat resistance (Japanese Patent Application Laid-open No. Hei 9-296144). However, silicone resins including silicone rubbers are expensive, and silicone rubbers have insufficient adherence to other substances and cannot significantly be adhered to other adherends unless a special adhesive is used. In addition, low-molecular-weight siloxane molecules contained in silicone rubbers evaporate with an elevating temperature and precipitate to the articles such as electrode of the electric circuits, thus causing contact failures and short circuits.